Essential component parts of a gas turbine are a compressor, a turbine with blades and at least one combustion chamber. The blades of the turbine are arranged on a shaft extending mostly through the entire gas turbine as a blade ring, said shaft being coupled to a consumer, like for instance a generator for power generation. The shaft provided with the blades is also known as turbine rotor or rotor. Guide vane rings which are used as nozzles to conduct the working medium through the turbine are disposed between the blade rings.
During operation of the gas turbine, the combustion chamber is supplied with compressed air from the compressor. The compressed air is mixed with a fuel, for instance oil or gas, and the mixture is burnt in the combustion chamber. The hot combustion exhaust gases are finally fed to the turbine as a working medium by way of a combustion chamber exit, whereby they transfer impulses to the blades upon decompression and cooling and thus perform work. The blades are used here to optimize the impulse transmission.
A typical burner assembly for gas turbines, as described in U.S. Pat. No. 6,082,111 and as used in particular in so-called tubular combustion chambers, generally comprises an annular support with nozzle lances distributed evenly about the periphery of the ring. Fuel nozzle openings are arranged in these nozzle lances, with which fuel can be injected into an air supply duct. The fuel nozzles represent a main stage of the burner, which is used to generate a premix flame, in other words a flame in which the air and the fuel are mixed prior to ignition. In order to minimize the NOx in the flame, premix burners with leaner air-fuel mixtures, in other words with mixtures which contain relatively little fuel, are operated.
A pilot burner, which is embodied as a diffusion burner, i.e. it generates a flame, with which the fuel is directly injected into the flame without previously being mixed with air, typically extends through the center of the annular fuel distribution ring. The pilot burner, as well as being used to start up the gas turbine, is also used to stabilize the premix flame, which is frequently operated in a range of the mixing ratio of the air to fuel in order to minimize the pollutant emissions, which may result in flame instabilities without a supporting pilot burner.
With high combustion temperatures, the fuel distribution ring is characterized by a short service life.